How to Couple Power Line Carrier Signal Onto Two Phase Power System

Hi All,

I have a situation where I need to put a 100KHz 13Vp-p carrier signal onto one of the two phase in a two phase powered system. Now I have tried this with no problem in single phase line to neutral system but this in this new application, only mostly two phase power systems is used (2 phase power is derived from 3 phase power, but the installation wiring only uses 2 phase with no neutral).

The power line carrier uses a propreitary amplitude modulation scheme for low bitrate data transmission over power line. Now

I have hunted around and can find nothing sensible for phase - phase coupling. There are alleged phase couplers available from the far east which MAY work and there are units that have outputs that you can couple to several phases but these seem to be bulky and quite expensive.

I came across a circuit which I think is a simple and straight forward way to couple the PL signal across 2 phase.

The DT is a differential transformer. For a 230V single phase, the line voltage will be sqroot(3)*230 = 398VAC. At the center tapped pri winding, the voltage across center tap and Phase A or B will be about 200VAC. Therefore, this should not exceed electrical rating for the PL coupling transformer which has been used in single phase applications before, right?

From the circuit, the DT transmits the difference signal between phase A and B across to its secondary which "converts" the 2 phase to single phase, with the PL coupling transformer on left providing the electrical isolation. The wiring arrangement of DT also serve to couple the PL carrier onto one phase (A) only with little to no PL carrier is being coupled onto phase B. Is this correct?

All I need to do is customize the DT transformer such each half of the primary winding (from center tap to phase A or B) can stand up to say 265VAC, in excess of 200VAC and the DT should work right? And for communications coupling transformer, the DT can be miniaturized further since it does not need to meet power requirements. Is this correct?

Can the above circuit work?

Many thanks!

Roy